Gearbox Lubrication

ABSTRACT

A gearbox including a housing; an input member rotatably supported in the housing; a rotatable shaft supported in the housing; gearing providing a power transmitting connection between the input member and the rotatable shaft; and an oil feed member held against rotation relative to the housing; wherein the oil feed member has at least one helical formation for causing oil within the gearbox to be fed axially of the oil feed member, on rotation of the rotatable shaft.

This invention relates to a gearbox for a vehicle, and in particular,but not exclusively, to a tail rotor gearbox for a helicopter.

The invention has innovative concepts that can be utilised in othertechnological fields, for example, automotive gearboxes, in a mannerthat will be appreciated.

In application to a tail rotor gearbox, more particularly, the inventionrelates to the lubrication of such a gearbox and specifically to thelubrication of a bearing assembly in such a gearbox by which a pitchcontrol shaft is moved axially within a hollow output shaft of thegearbox through the action of an actuating member. The output shaftcarries the tail rotor of the helicopter, and the pitch control shaft isconnected to the tail rotor in such a way as to vary, collectively, thepitch of its blades as the pitch control shaft is moved axially relativeto the output shaft. Although movable axially therein, the pitch controlshaft rotates with the output shaft, and the actuating member, whichdoes not rotate but which is movable in the direction in which the pitchcontrol shaft moves within the output shaft, has to be connected to thepitch control shaft by way of a thrust bearing assembly which is able totransmit axial forces in both directions between the rotating pitchcontrol shaft and the (non-rotating) actuating member.

In a conventional helicopter, the tail rotor gearbox transmits powerbetween a drive shaft assembly which extends longitudinally of thehelicopter, from the engine(s) and transmission in the vicinity of themain rotor of the helicopter, to the tail rotor. The output shaft of thegearbox, on which the tail rotor is mounted, extends transversely of thehelicopter. The gearbox includes gearing, e.g. a crown wheel and pinionarrangement which provides for power transmission between the outputshaft and an input member whose axis of rotation is at leastsubstantially at right angles to the axis of rotation of the outputshaft, the input member of the gearbox being connected to thelongitudinal drive shaft assembly of the helicopter. The gearboxprovides a reduction gearing transmission ratio between the driveshaftand output shaft.

In a tail rotor gearbox utilised by the present applicant in some of itshelicopters, the thrust bearing assembly, by which movement of theactuating member in the direction axially of the output shaft istransmitted to the pitch control shaft, is disposed within an end partof the pitch control shaft within the output shaft. One potentialproblem associated with such disposition of the bearing assembly is thatof lubrication thereof, since any oil in the vicinity of the axis ofrotation of the output shaft is centrifuged outwardly from such axis asthe output shaft rotates. Without adequate lubrication, the service lifeof the bearing assembly may be curtailed.

The present invention addresses the problem of lubrication of such abearing assembly.

According to a first aspect of the present invention, we provide ahelicopter tail rotor gearbox including:

-   -   a housing;    -   an output shaft for connection to a tail rotor rotatably        supported in the housing and having an open end therein;    -   an input member rotatably supported in the housing;    -   gearing providing a power transmitting connection between the        input member and output shaft;    -   a pitch control shaft for effecting a change in the pitch of the        tail rotor, the pitch control shaft being disposed at least        partially within the output shaft, rotatable therewith, and        movable relative thereto along the rotational axis of the output        shaft;    -   an actuating member for effecting axial movement of the pitch        control shaft, the actuating member being movable axially of the        output shaft but held against rotation therewith; and    -   a bearing assembly positioned in between the pitch control shaft        and the actuating member for permitting relative rotation        therebetween;    -   wherein the gearbox includes at least one formation for        diverting oil, dispersed within the housing in use, towards the        open end of the output shaft.

According to a second aspect of the invention, we provide a helicopterincluding a gearbox according to the first aspect of the invention.

According to a third aspect of the invention, we provide a helicoptertail rotor system including a gearbox according to the first aspect ofthe invention.

The gearbox may have an oil feed member held for co-operation with theoutput shaft at or adjacent the open end thereof and/or with the pitchcontrol shaft, and adapted on relative rotation between the oil feedmember and output shaft to cause oil to be fed axially to the vicinityof the bearing assembly.

The oil feed member may have at least one helical formation for causingoil to be fed axially on relative rotation between the oil feed memberand a surface co-operating therewith.

The oil feed member may have an external peripheral surface which liesin close proximity to an internal surface of the output shaft, theperipheral surface of the oil feed member being provided with thehelical formation(s) to cause oil to be fed axially of the output shafton relative rotation between the output shaft and oil feed member.

The oil feed member may be held against rotation by being supported onthe actuating member.

The at least one formation for diverting oil to the open end of theoutput shaft may include a deflecting member for deflecting oil from anupper part of the housing interior towards a region adjacent to the openend of the output shaft.

The output shaft may have a formation for retaining oil within theinterior of the output shaft and preferably the oil feed member fluidlycommunicates with the oil retaining formation.

The gearbox may include an oil catcher member with a drainage channelformation for catching oil from the at least one formation for divertingoil. The drainage channel formation may extend radially from aperipheral surface of the oil catcher member towards the rotational axisof the output shaft. Preferably the oil catcher member further includesa further formation in fluid communication with the drainage channelformation for directing caught oil towards the open end of the outputshaft. The further directing formation may communicate with theformation for retaining oil within the interior of the shaft andpreferably includes a frusto-conical formation.

According to a fourth aspect of the invention, we provide a gearboxincluding:

-   -   a housing;    -   an input member rotatably supported in the housing;    -   a rotatable shaft supported in the housing;    -   gearing providing a power transmitting connection between the        input member and the rotatable shaft; and    -   an oil feed member held against rotation relative to the        housing;    -   wherein the oil feed member has at least one helical formation        for causing oil within the gearbox to be fed axially of the oil        feed member, on rotation of the rotatable shaft.

According to a fifth aspect of the invention, we provide a vehicleincluding a gearbox according to the fourth aspect of the invention.

The rotatable shaft may have an open end therein and the oil feed memberis positioned in an interior portion of the rotatable shaft.

In use, the oil feed member may cause oil dispersed within the housingto be fed into the interior of the rotatable shaft or cause oil withinthe rotatable shaft to be fed into an interior of the housing.

The gearbox may include at least one formation for diverting oil towardsthe oil feed member. The at least one formation for diverting oil mayinclude a deflecting member for deflecting oil from a remote part of thehousing towards the oil feed member.

The oil feed member may have an external peripheral surface on which theat least one helical formation is formed, the external peripheralsurface lying in close proximity to an internal surface of the rotatingshaft.

The oil feed member may be supported on a member which is held againstrotation relative to the rotatable shaft.

The rotatable shaft may have a formation for retaining oil within theinterior of the rotatable shaft and preferably the oil feed memberfluidly communicates with the oil retaining formation.

The gearbox may further include an oil catcher member with a drainagechannel formation for catching oil from an interior of the housing. Theoil catcher drainage channel formation may catch oil from the at leastone formation for diverting oil. The drainage formation preferablyextends radially from a peripheral surface of the oil catcher membertowards the rotational axis of the rotatable shaft. The oil catchermember may include a further formation in fluid communication with thedrainage channel formation for directing caught oil towards the interiorportion of the rotatable shaft. The further directing formation maycommunicate with the formation for retaining oil within the interior ofthe shaft and preferably comprises a frusto-conical formation.

These and other features of the invention will now be described by wayof example with reference to the accompanying drawings of which:

FIG. 1 is a sectional illustration of a tail rotor gearbox to which theinvention has been applied,

FIG. 2 is an enlargement of part of FIG. 1,

FIG. 3 is an exploded perspective view of parts of the gearbox,

FIG. 4 is a perspective view of a further part of the gearbox.

Referring to the drawings, the illustrated gearbox is a tail rotorgearbox that comprises a housing indicated generally at 10. The housingcomprises a number of housing parts secured together by screw-threadedfastenings at joint faces therebetween, the housing including anelongate, tapering, first part 12, a second part 14, an end cover part16 and a side part 18. The side part 18 carries a bearing-supportingstructure 20, which supports, by way of two oppositely-oriented taperroller bearing assemblies only one of which is indicated at 22, an inputmember 24 having a pinion gear 26 inside the housing of the gearbox.Outside the housing, the input member 24 carries a drive flange (notshown) or other element for connection to a tail rotor drive shaftassembly.

In the interior of the housing 10, the housing part 12 carries abearing-support member 30 containing oppositely-oriented taper rollerbearings whose outer races are supported in the member 30. The innerraces of the bearings 32, 34 are received on the exterior surface of ahollow gearbox output shaft 36 which is provided, adjacent its free endwithin the gearbox housing 10, with a flange part 38 to which isfastened a crown wheel gear 40, having teeth which mesh with the teethof the pinion gear 26 so as to provide a reduction gear ratio betweenthe input member 24 and output shaft 36 of the gearbox. The output shaft36 rotates by the gearing connecting the input member 24 to the outputshaft 36. The other end of the output shaft 36 extends through thecasing part 12 and is supported by another bearing or bearings notshown, the shaft emerging from the gearbox housing 10 and being adaptedfor carrying a tail rotor assembly, also not shown.

Within the output shaft 36 there is disposed a pitch control shaft 44.This is movable relative to the output shaft 36 in the direction of therotational axis of the output shaft 36, but it rotates with the outputshaft 36, having a splined connection with the interior thereof.

Adjacent the end of pitch control shaft 44 within the gearbox housing10, a thrust bearing assembly indicated generally at 46 in FIG. 1, andvisible in greater detail in FIG. 2 of the drawings, is provided. Thethrust bearing assembly 46 is a double row bearing assembly with barrelshaped rollers arranged in two oppositely inclined rows. The outer race48 of the thrust bearing assembly 46 is held in a seating 50 of theshaft 44, while the inner race 52 of the thrust bearing assembly 46receives, and is held on, a shaft portion 54 extending axially from anactuating member 56 (FIG. 3). The remainder of the actuating member 56comprises a body 58 with a splined bore 60 extending into the body fromits free end. The external surface of the body 58, outside the splinedbore 60 (the splines in the bore 60 not being shown in FIG. 3) isprovided with a number of circumferentially spaced axially-extendinggrooves 62. The actuating member 56 is held against rotation relative tothe housing 10.

An oil feed member 63 is carried by the body 58 of the actuating member56. This is an annular component, having a cylindrical central bore 64which fits on the external cylindrical surface of the body 58. Thevisible end face 66 of the oil feed member 63 is provided with a numberof circumferentially spaced axially and radially extending recesses 68,some of which are engaged by radially outwardly extending tabs 70 on alocking washer 72, the locking washer also having one or more inwardlyextending tabs 74 engageable in a respective one or more of the grooves62 on the actuating member 56. Hence the oil feed member 63 is heldagainst rotation relative to the actuating member 56 and the housing 10.The oil feed member 63 is stationary during operation of the gearbox. Aretaining ring, e.g. a “Spirolox”™ retaining ring, 76, is engaged in anannular undercut groove 78 adjacent the end face 66 of the oil feedmember 63, retaining the locking washer 72 in the interior of the oilfeed member 63.

The external surface 80 on a peripheral portion of the oil feed member63 lies in close proximity to the interior cylindrical surface of theoutput shaft 36 surrounding it. The surface 80 of the oil feed member 63is provided with at least one helical groove 82 of such width, depth,and hand as to cause oil in the vicinity thereof, when the output shaft36 is rotating in use but the oil feed member 63 not rotating, to be fedaxially to the right hand side of the oil feed member 62, having regardto the orientation in which it is shown in the drawings. In other words,such feed of oil is towards the thrust bearing assembly 46.

If more than one helical groove 82 is provided in the surface 80, thegrooves may be arranged in the manner of a multi-start screw thread.

Adjacent the free end of the output shaft 36, beyond the oil feed member63, an undercut annular recess within the output shaft 36 accommodates amember 86 having an annular radially inwardly extending wall formation.The effect of the member 86 is to retain a small quantity of oil in theinterior of the output shaft 36, as a pool at its lowermost part whenthe output shaft 36 is not rotating, or as a film around its innersurface under centrifugal action when the output shaft 36 is rotating.Such oil contacts the oil feed member 63, to be fed towards the thrustbearing assembly 46 by the action of the helical formation on theperipheral surface of the oil feed member 63.

To aid retention of oil in the interior of the output shaft 36, so thatthe oil can be moved towards the thrust bearing assembly 46 asaforesaid, an oil catcher member 90, shown in FIG. 4 of the drawings, isheld within the housing of the gearbox, inside the end cover part 16 andfacing the open end of the output shaft 36.

An external flange 92 of the oil catcher member 90 is held between jointfaces of the respective housing parts 14, 16. The oil catcher member 90has a central aperture 94 through which the output member (not shown) ofan actuator assembly (not shown), but disposed outside the housing part16, extends, such an output member having a splined end portion whichengages the splined bore 60 of the actuating member 56. This preventsthe actuating member 56 and components carried thereby from rotating.The output member of the actuator assembly causes displacement of thepitch control shaft 44, moved through the intermediary of the actuatingmember 56 and thrust bearing assembly 46, axially relative to thegearbox output shaft 36, thereby effecting collective control of thepitch of the tail rotor blades.

The oil catcher member 90 has an oil-catching drainage channel formation98 extending at an inclination downwardly, from its peripheral regionfacing the crown wheel 40, towards the central aperture 94. The channel98 leads into a somewhat frusto-conical directing formation 100,discharging oil from an end portion 102 of the formation 100, which endportion lies within the end of the output shaft 36 beyond the member 86.An oil deflecting member 104 is provided within the housing part 14 at aremote part of the housing, adjacent the upper part of the housing andgenerally above part of the periphery of the crown wheel 40, so as todeflect oil thrown centrifugally around the interior of the housingtowards the channel 98 of the oil catcher member 90.

In use, by virtue of the operation of the oil feed member 63 and thesupply of oil thereto by the oil deflector member 104 and the oilcatcher member 90, is to ensure that the thrust bearing assembly 46 iseffectively lubricated. However, it will be appreciated that the oildeflector member 104 can be used independently of the oil catcher member90 and the oil feed member 63 to deliver oil to the interior of theoutput shaft 36 and thereby lubricate the thrust bearing assembly 46.Furthermore, the oil catch member 90 can be used in conjunction with theoil deflector member 104 to aid in lubrication of the thrust bearingassembly 46. The oil deflector member 104 may be in co-operation withother features well known in the art for channelling oil so as todeflect oil from a remote part of the housing to an intended region.

It will be appreciated that the concept of using a stationary oil feedmember together with other rotatable surfaces has application in manytechnological fields, e.g. aviation gearboxes, automotive gearboxes. Inan alternative mode of operation, the oil feed member may also beutilised to cause oil within the rotatable shaft/output shaft to be fedinto an interior of the housing. In other words, the oil feed member canbe configured to cause oil to flow in either direction by altering thedirection of the rotatable shaft or the configuration of the helicalchannel on the surface of the oil feed member.

The oil feed member 63 may conveniently be a moulding of a suitableplastics material, e.g. PEEK (polyether ether ketone).

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

Further features of one or more aspects of the invention are set out inthe numbered clauses provided below.

Clauses

1. A helicopter tail rotor gearbox including:

-   -   a housing;    -   an output shaft for connection to a tail rotor rotatably        supported in the housing and having an open end therein;    -   an input member rotatably supported in the housing; gearing        providing a power transmitting connection between the input        member and output shaft;    -   a pitch control shaft for effecting a change in the pitch of the        tail rotor, the pitch control shaft being disposed at least        partially within the output shaft, rotatable therewith, and        movable relative thereto along the rotational axis of the output        shaft;    -   an actuating member for effecting axial movement of the pitch        control shaft, the actuating member being movable axially of the        output shaft but held against rotation therewith; and    -   a bearing assembly positioned in between the pitch control shaft        and the actuating member for permitting relative rotation        therebetween;    -   wherein the gearbox includes at least one formation for        diverting oil, dispersed within the housing in use, towards the        open end of the output shaft.

2. A gearbox according to clause 1 further including an oil feed memberheld for co-operation with the output shaft at or adjacent the open endthereof and/or with the pitch control shaft, and adapted on relativerotation between the oil feed member and output shaft to cause oil to befed axially to the vicinity of the bearing assembly.

3. A gearbox according to clause 2 wherein the oil feed member has atleast one helical formation for causing oil to be fed axially, onrelative rotation between the oil feed member and a surface co-operatingtherewith.

4. A gearbox according to clause 3 wherein the oil feed member has anexternal peripheral surface lying in close proximity to an internalsurface of the output shaft, the peripheral surface of the oil feedmember being provided with the helical formation(s) for causing axialfeeding of oil on relative rotation between the output shaft and oilfeed member.

5. A gearbox according to any one of the preceding clauses wherein theoil feed member is held against rotation by being supported on theactuating member.

6. A gearbox according to any one of the preceding clauses wherein theat least one formation for diverting oil to the open end of the outputshaft includes a deflecting member for deflecting oil from an upper partof the housing interior towards a region adjacent to the open end of theoutput shaft.

7. A gearbox according to any one of the preceding clauses wherein theoutput shaft has a formation for retaining oil within an interior of theoutput shaft.

8. A gearbox according to clause 7, when appendent to clause 2, whereinthe oil feed member fluidly communicates with the oil retainingformation.

9. A gearbox according to any preceding clause further comprising an oilcatcher member with a drainage channel formation for catching oil fromthe at least one formation for diverting oil.

10. A gearbox according to clause 9 wherein the drainage formationextends radially from a peripheral surface of the oil catcher membertowards the rotational axis of the output shaft.

11. A gearbox according to clause 9 or 10 the oil catcher memberincluding a further formation in fluid communication with the drainagechannel formation for directing caught oil towards the open end of theoutput shaft.

12. A gearbox according to clause 11 when appendent to either clause 7or 8 wherein the further directing formation communicates with theformation for retaining oil within the interior of the shaft.

13. A gearbox according to clause 11 or 12 wherein the further directingformation includes a frusto-conical formation.

14. A helicopter including a gearbox according to any one of thepreceding clauses.

15. A helicopter tail rotor system including a gearbox according to anyone of clauses 1 to 13.

16. A gearbox including:

-   -   a housing;    -   an input member rotatably supported in the housing;    -   a rotatable shaft supported in the housing;    -   gearing providing a power transmitting connection between the        input member and the rotatable shaft; and    -   an oil feed member held against rotation relative to the        housing;    -   wherein the oil feed member has at least one helical formation        for causing oil within the gearbox to be fed axially of the oil        feed member, on rotation of the rotatable shaft.

17. A gearbox according to clause 16 wherein the rotatable shaft has anopen end therein and the oil feed member is positioned in an interiorportion of the rotatable shaft.

18. A gearbox according to clause 16 or 17, wherein, in use, the oilfeed member causes oil dispersed within the housing to be fed into theinterior of the rotatable shaft.

19. A gearbox according to clause 16 or 17, wherein, in use, the oilfeed member causes oil within the rotatable shaft to be fed into aninterior of the housing.

20. A gearbox according to any one of clauses 16 to 19 wherein thegearbox includes at least one formation for diverting oil towards theoil feed member.

21. A gearbox according to clause 20, wherein the at least one formationfor diverting oil includes a deflecting member for deflecting oil from aremote part of the housing towards the oil feed member.

22. A gearbox according to any one of clauses 16 to 21 wherein the oilfeed member has an external peripheral surface on which the at least onehelical formation is provided, the external peripheral surface lying inclose proximity to an internal surface of the rotating shaft.

23. A gearbox according to any one of clauses 16 to 22 wherein the oilfeed member is supported on a member which is held against rotationrelative to the rotatable shaft.

24. A gearbox according to any one of clauses 16 to 23 wherein therotatable shaft has a formation for retaining oil within the interior ofthe rotatable shaft.

25. A gearbox according to clause 24 wherein the oil feed member fluidlycommunicates with the oil retaining formation.

26. A gearbox according to any one of clauses 16 to 25, furtherincluding an oil catcher member with a drainage channel formation forcatching oil from an interior of the housing.

27. A gearbox according to clause 26, when appendent to clause 21,wherein oil catcher drainage channel formation catches oil from the atleast one formation for diverting oil.

28. A gearbox according to clause 27 wherein the drainage formationextends radially from a peripheral surface of the oil catcher membertowards the rotational axis of the rotatable shaft.

29. A gearbox according to any one of clauses 26 to 28 wherein the oilcatcher member includes a further formation in fluid communication withthe drainage channel formation for directing caught oil towards theinterior portion of the rotatable shaft.

30. A gearbox according to clause 29, when appendent to clause 24 or 25wherein the further directing formation communicates with the formationfor retaining oil within the interior of the shaft.

31. A gearbox according to clause 29 or 30 wherein the further directingformation comprises a frusto-conical formation.

32. A vehicle including a gearbox according to any one of clauses 16 to31.

33. A gearbox substantially as hereinbefore described with reference toand as shown in the accompanying drawings.

34. Any novel feature or novel combination of features described hereinand/or in the accompanying drawings.

1. A gearbox including: a housing; an input member rotatably supportedin the housing; a rotatable shaft supported in the housing; gearingproviding a power transmitting connection between the input member andthe rotatable shaft; and an oil feed member held against rotationrelative to the housing; wherein the oil feed member has at least onehelical formation for causing oil within the gearbox to be fed axiallyof the oil feed member, on rotation of the rotatable shaft.
 2. Thegearbox according to claim 1 wherein the rotatable shaft has an open endtherein and the oil feed member is positioned in an interior portion ofthe rotatable shaft.
 3. The gearbox according to claim 1, wherein, inuse, the oil feed member causes oil dispersed within the housing to befed into the interior of the rotatable shaft.
 4. The gearbox accordingto claim 1, wherein, in use, the oil feed member causes oil within therotatable shaft to be fed into an interior of the housing.
 5. Thegearbox according to claim 1 wherein the gearbox includes at least oneformation for diverting oil towards the oil feed member.
 6. The gearboxaccording to claim 5, wherein the at least one formation for divertingoil includes a deflecting member for deflecting oil from a remote partof the housing towards the oil feed member.
 7. The gearbox according toclaim 1 wherein the oil feed member has an external peripheral surfaceon which the at least one helical formation is provided, the externalperipheral surface lying in close proximity to an internal surface ofthe rotating shaft.
 8. The gearbox according to claim 1 wherein the oilfeed member is supported on a member which is held against rotationrelative to the rotatable shaft.
 9. The gearbox according to claim 1wherein the rotatable shaft has a formation for retaining oil within theinterior of the rotatable shaft.
 10. The gearbox according to claim 9wherein the oil feed member fluidly communicates with the oil retainingformation.
 11. The gearbox according to claim 6, further including anoil catcher member with a drainage channel formation for catching oilfrom an interior of the housing.
 12. gearbox according to claim 11,wherein the oil catcher drainage channel formation catches oil from theat least one formation for diverting oil.
 13. The gearbox according toclaim 12 wherein the drainage channel formation extends radially from aperipheral surface of the oil catcher member towards the rotational axisof the rotatable shaft.
 14. The gearbox according to claim 11 whereinthe oil catcher member includes a further formation in fluidcommunication with the drainage channel formation for directing caughtoil towards the interior portion of the rotatable shaft.
 15. The gearboxaccording to claim 14, wherein the further formation communicates with aformation for retaining oil within the interior of the rotatable shaft.16. The gearbox according to claim 14 wherein the further formationcomprises a frusto-conical formation.
 17. A vehicle including a gearboxaccording to claim
 1. 18. The gearbox according to claim 15 wherein theoil feed member fluidly communicates with the oil retaining formation.19. The gearbox according to claim 18 wherein the further formationcomprises a frusto-conical formation.
 20. The gearbox according to claim15 wherein the further formation comprises a frusto-conical formation.